There are many types of cargo containers. Cargo containers have been designed to be loaded onto ocean going ships. Certain cargo containers have been specially shaped to fit into the curved hulls of airplanes. Cargo containers have also been specifically designed to be transported by train. Cargo containers are also often transported as trailers by trucks.
There are many challenges associated with cargo containers. One problem is that cargo containers are often made up of many different parts. Increased numbers of parts often add to the cost and manufacturing time of the cargo container. Thus it is desirable to have a cargo container with as little complexity as possible.
Another problem is that the mass of the container must be transported along with the cargo. Heavy containers require more energy and cost to be transported than light containers. Wind resistance further acts upon cargo containers in transit. A drag force acts on an object which moves in a fluid environment such as air or water. Drag forces on the trailer reduce the fuel efficiency of a truck pulling a cargo container, and increase the cost of transporting the cargo container. Smooth sided containers with rounded edges reduce air resistance and reduce transportation costs. Smooth sided containers also facilitate the application of decals and advertisements to the side of the container. It is desirable have a light and aerodynamic cargo container to reduce transportation costs.
Another problem is that cargo containers must be resilient enough to carry cargo without being significantly distorted and damaging the cargo. Cargo containers are subjected to strain and forces during loading, unloading, and transport. Thus it is desirable to have a cargo container that is as resilient as possible.
There have been attempts to solve some of these problems. For example, U.S. Pat. No. 3,557,992 that issued to Reeves teaches “a method and apparatus for molding insulated reinforced plastic structures for use as refrigerated cargo containers and truck or trailer bodies. The insulated reinforced plastic structures have substantially parallel opposed sides and are molded as a unitary structure in a single molding operation. Glass fiber reinforcing materials, which include an insulating core material, are placed in the bottom of a female mold and up against the sides. A somewhat loose fitting mandrel braced vertically but which may be later be expanded laterally, is lowered down in between the materials at the side and on top of materials at the bottom. Further glass fiber reinforcing materials, including a core material are placed on top of the mandrel. A male mold is lowered in place on top of these materials but somewhat short of full final closing. A free flowing liquid plastic resin is pumped within the space defined by the make and female molds and the mandrel. The free flowing liquid plastic resin impregnates the glass fiber reinforcing and wets the surfaces of the core material. The male mold is closed fully downward and the mandrel expanded fully laterally, compressing the glass fiber reinforcing and compacting the entire material assembly in its final form. The liquid plastic resin then hardens, the molds are opened, and the molding is removed from the mold.”
For example, U.S. Pat. No. 5,026,447 that issued to O'Connor teaches “an article of manufacture comprising a pultruded thermoplastic composite body having at least two integral sections of different cross-sectional shapes. This is produced by a method and/or in an apparatus wherein an elongated body of reinforced thermoplastic material is pulled through a plurality of dies and the plurality of dies are operated independently of each other so that any combination of the dies can be selected to operate on the elongated body for imparting to at least a portion of the body the cross-sectional shape of the selected one or ones of the dies.”
U.S. Pat. No. 5,286,320 that issued to McGrath teaches “a method for continuously manufacturing a composite sandwich structure by pultrusion through a pultrusion die comprises arranging fiber reinforcement materials on the surface of a preformed foam core, applying liquid resin to the reinforcement materials on the surface of the foam core, heating the surface region of the foam core to a temperature of at least 100° C. to convert water in the foam core to steam, thereby causing water vapor pressure expansion of the foam, and using the expansion of the foam core to subject the liquid resin to increased pressure.”
U.S. Pat. No. 5,556,496 that issued to Sumerak teaches “a method for producing a pultrusion product having a variable cross-section using a specially adapted temperature controllable pultrusion die includes the steps of pulling reinforcing fibers which have been impregnated with a heat curable thermosetting polymeric resin composition through a temperature controllable die, heating the temperature controllable die to a temperature sufficient to effect curing of the thermosetting resin, cooling the temperature controllable die to a temperature which is sufficiently low to prevent any significant curing of thermosetting resin passing through the pultrusion die, pulling the cured material and a predetermined length of uncured material from the die, reshaping the uncured material, and curing the reshaped material. The reshaping step can be used to provide off-sets, flanges, bosses and the like. The method and associated apparatus of the invention provide a relatively simple and inexpensive way of producing fiber-reinforced thermoset plastics having a variable cross-section selected intervals along the length of the article.”
U.S. Pat. No. 6,558,608 that issued to Haraldsson teaches “a method of constructing large, unitary, fiber-reinforced Polymer composite containers using a vacuum assisted resin transfer molding process. The method allows for the construction of container systems with only two separately molded parts—an open box consisting of a base (i.e., floor), 2 sidewalls and 2 endwalls, and a cover (i.e., roof). The method results in a structure which maintains the continuity of the reinforcement fibers across the junction between the floor, side, and end walls corners. This method can be applied to very large composite structures such as railcar bodies, intermodal containers, and shelters.”
U.S. Pat. No. 6,565,976 that issued to Qureshi teaches “a pultrusion resin composition comprising about 75 wt % to about 85 wt % of a phenolic resin, about 9 wt % to about 20 wt % of the reaction product of a polyhydroxy compound and an epoxy-functional polysiloxane, about 6 wt % to about 15 wt %, of a phenolic epoxy, and about 0.2 wt % to about 1 wt % of a catalyst, based on total weight of the composition. Pultruded products are formed by drawing fibrous reinforcement through a bath of the pultrusion resin composition.”
U.S. Pat. App. Pub. No. 20020014302 by Fanucci teaches “a pultrusion method produces a composite structural member having rigid elements embedded therein. The structural member may be a sandwich structure in which one or more rigid, pre-rigidized, or rigidizable composite or non-composite structural elements are introduced at regular or irregular positions within core elements. The structural member may also be formed from layers of resin-matrix fiber fabric into a structural cross-section, such as an I-beam or T-beam, with a bundle of pre-pultruded rods located at the bends or the web-flange intersection points within layers.”